The easiest way is through brokerage connection, which is explained in our Brokerage Connection Help. Another option is to import a file from your brokerage, as explained here. For users that trade at Fidelity, Schwab and TD Ameritrade, Stock Rover supports direct import of their exported data. More brokerage houses will be supported in the future. Note that TD Ameritrade exports their CSV file with an XLS extension. It is OK to to import the XLS file in this specific case.
For other sources, you can import by specifying a CSV (comma separated values) file. You can create a CSV file from a spreadsheet program such as Excel, or by using the export function from your brokerage firm. To be correctly read by Stock Rover, the CSV file should have three columns: Symbol, Buy Price and Quantity. Each row should represent a security in your portfolio.